Clemson researchers closer to developing heat-tolerant soybeans

CLEMSON – Soybean is one of the top cash crops grown in South Carolina and some Clemson University researchers have helped discover an “important milestone” in developing heat-tolerant soybeans.

The team is led by Sruthi Narayanan, an assistant professor and researcher in the Clemson Department of Plant and Environmental Sciences. The researchers are examining traits that lead to heat tolerance in soybean.

A paper about their study, Comparative Lipidomic Analysis Reveals Heat Stress Responses of Two Soybean Genotypes Differing in Temperature Sensitivity, appears in the April 4 edition of the Plants journal.

“Our study found novel lipid metabolic traits associated with heat tolerance in soybean and the genes controlling those traits,” Narayanan said. “These genes can lead to the identification of molecular markers that will be useful for selecting for heat-tolerant soybean genotypes. Identifying tightly linked molecular markers for stress tolerance is an important accomplishment in stress-tolerance research and a milestone in variety development projects.”

Soybeans typically are planted in the Southeast from May 10 to July 11 and harvested from Oct. 20 to Dec. 30. Some growers are adopting early-maturing varieties that are planted in April and harvested during the hottest parts of the summer. This is known as an Early Soybean Production System (ESPS). This system originated in Mississippi but has gained interest in other areas of the Southeast. However, with ESPS, high temperatures at harvest can cause problems with seed quality, wrinkled seed, decreased germination and so on, says Ben Fallen, a former Clemson soybean breeder and now a soybean breeder with the United States Department of Agriculture’s Agricultural Research Service, who also is working on the project.

“Early maturing soybeans will not wait around to be harvested,” Fallen said. “Seed quality will go down in a hurry, especially if the weather doesn’t cooperate with harvest. Not only that, but seed production can be a problem with beans planted anytime during the typical planting window, if the plants are setting pods during the heat of the summer and there is no rain in sight, seed quantity and quality will be a problem.”

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During the study, the researchers investigated whether lipid metabolic changes contribute to differences in heat stress responses in a heat-tolerant soybean variety and a heat-susceptible soybean variety. The heat-susceptible variety was developed for the ESPS in Mississippi.

“The lipid trait and related genes that contribute to heat tolerance in [heat-tolerant soybean] can be incorporated into other genotypes that can be grown in South Carolina,” Narayanan said. “This will be valuable for developing heat-tolerant soybean varieties adapted to our conditions”.

The researchers wanted to determine what changes take place in soybean leaves when subjected to high temperatures. They found a decline in fats that are undesirable for biodiesel and cooking oil as they reduce stability and keeping quality. On the other hand, high-fat soybeans have added value, primarily due to health benefits.

While the researchers consider this discovery as valuable for the soybean industry, they agree more research is needed.

“What we hope is that this translates to being able to develop more heat-tolerant soybean lines and as an added bonus, may also have an improved oil composition,” says Sachin Rustgi, a molecular breeder at the Clemson Pee Dee Research and Education Center, who also is part of the project team. “There is more to gain from knowing the whole picture, which is why it is so important to work together as a team of scientists, in multiple fields, to work towards sustainable agriculture.”

In addition to Narayanan, Fallen and Rustgi, other researchers include Zolian Zoong-Lwe, a graduate research assistant in the Clemson Department of Plant and Environmental Sciences, Nitant Gandhi of NCJ Diagnostics and DNA Technologies in Monmouth Junction, New Jersey; Ruth Welti of the Kansas Lipidomics Research Center at Kansas State University, and Rusty Smith of the United States Department of Agriculture’s Agricultural Research Service Crop Genetics Research Unit in Stoneville, Mississippi.

Soybeans are a major crop grown in South Carolina. According to the USDA National Agricultural Statistics Service, 320,000 acres of soybeans were harvested in the state in 2019. A total of 363,000 acres of corn were harvested and 297,000 acres of cotton were harvested in South Carolina.

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